In recent years, low-power display units (displays) with high image quality have been in increasing demand, as mobile equipment such as mobile telephones and portable information terminals has become widespread. In particular, recently, electronic book delivery businesses have started, and a display having display quality suitable for reading purpose has been desired.
As such a display, various displays such as a cholesteric liquid crystal display, an electrophoretic display, an electric-redox-type display, and a twisting ball display have been proposed. For reading purpose, reflection-type displays are advantageous. In the reflection-type displays, bright display is performed using reflection (diffusion) of outside light in a manner similar to that of paper and thus, display quality close to that of paper is achieved.
Among the reflection-type displays, an electrophoretic display utilizing an electrophoretic phenomenon has a high response speed while consuming low power, and thus is expected as a strong candidate. As a display method thereof, mainly the following two methods have been proposed.
A first method is a method in which two kinds of charged particles are dispersed in an insulating liquid, and the charged particles are moved in response to an electric field. These two kinds of charged particles are different from each other in terms of optical reflection properties, and are also of opposite polarity. In this method, an image is displayed by a change in distribution of the charged particles in response to an electric field.
A second method is a method in which charged particles are dispersed in an insulating liquid, and a porous layer is disposed in the insulating liquid (for example, Patent Literature 1). In this method, the charged particles move through pores of the porous layer in response to an electric field. The porous layer may include, for example, a fibrous structure made of a polymer material, and non-migrating particles that are held in this fibrous structure and different from the charged particles in terms of optical reflection properties.